Cuff-less, portable devices do not accurately measure blood pressure
Portable health devices and smartwatches that measure blood pressure (BP) without the use of a cuff may not yield sufficiently accurate results, according to a new study.
“The Everlast smartwatch and the BodiMetrics Performance Monitor we tested are not accurate enough to be used as BP measurement devices,” said researchers. “The continued sale of these and similar, non-FDA-approved cuff-less BP measurement devices is a public health concern that should be addressed.”
The BPs of 85 patients (mean age, 53±21 years; 42 percent female) were measured using the Everlast smartwatch and the BodiMetrics monitor, and the corresponding results were compared against those of a standard, hospital-grade, automated sphygmomanometer. Thirty-two (38 percent) patients had self-reported hypertension, and only one of whom was not taking antihypertensive medication. [Hosp Pract 2019;doi:10.1080/21548331.2019.1656991]
Figures obtained from the BodiMetrics Performance Monitory showed good and significant correlation with reference measurements (ρ, 0.88; p<0.01), though results were only obtained for systolic BP, as the device does not measure diastolic BP. The absolute BP difference between the two methods was 5.3±4.7 mm Hg.
The Everlast smartwatch, on the other hand, despite collecting values for both systolic and diastolic BP, did not show such fidelity to the hospital-grade measurements. There were discrepancies of 16.9±13.5 and 8.3±6.1 mm Hg for systolic and diastolic BP, respectively, between the smartwatch and reference devices.
Researchers also observed a link between the absolute discrepancies in the Everlast watch measurements and the BP value. Specifically, the watch estimated lower systolic BP values to be higher, while higher values were estimated to be lower (ρ, –0.45; p<0.01).
The two test devices also fell short in terms of the determination of hypertension. For instance, the BodiMetrics Performance Monitor identified only 80 percent of all hypertensive reference systolic BP measurements, while the Everlast watch identified none.
“In order for a cuff-less BP monitor to be safe for consumer use it should operate accurately over a range of pressures after being calibrated at a certain pressure, but this concept is not tested when using current validation protocols,” researchers explained “The current protocols also do not assess whether calibration of cuff-less devices remains appropriate after a significant time period has passed since initial calibration.”
In the present study, it was shown that both test devices were not accurate enough to pass as BP measurement devices, they added, noting that while the BodiMetrics monitor yielded better measurements, the device still fell short of current accuracy guidelines.
Moreover, as these tests were performed under static conditions, “it seems highly unlikely that they would perform better either at a range of BPs different from the calibration value, or after a significant time period since initial calibration,” the researchers pointed out.
Importantly, the findings of the present study point to a public health concern in need of greater regulatory attention, they added. “Widespread use of these devices likely results in the misclassification of patients with hypertension as normotensive, potentially resulting in a delayed diagnosis of hypertension or incorrect self-medication adjustment by patients with known hypertension.”